Malignant brain tumors represent one of the most refractory cancers to therapy and remain incurable. Gliomas represent the most common type of brain tumors and occur in various grades, with the patient's prognosis inversely proportional to grade. Radiotherapy remains a major component of treatment modalities for controlling both malignant and benign meningiomas. In patients with residual or recurring benign tumors, there is increasing concern about radiation-related side effects that may occur even with highly accurate therapies such as radiosurgery. Despite some therapeutic effect, recent evidence has shown that irradiation may promote malignant behaviors of cancer cells both in vitro and in vivo by activating several pathways involved in tumor invasiveness, angiogenesis and metastasis. Several studies, including ours, demonstrated significantly increased levels of MMP-2 in malignant gliomas or glioblastomas. We hopothesize that the MMP-2 gene will be targeted while simultaneously combined with radiation and their anti-cancer effects will be determined. The specific aims of this proposal are: Specific Aim 1. Evaluate the effect of p-MMP-2 construct and irradiation alone, or in combination, on glioma cell growth, invasion and angiogenesis in both in vitro and in vivo models. Aim 1a. Determine the effect of p-MMP-2 and irradiation alone, or in combination, on the levels of MMP-2 in glioblastoma cell lines. Aim 1b. Determine the effect of p-MMP-2 and irradiation alone, or in combination, on the invasive behavior of human glioblastoma cell lines in in vitro models with that of controls/mock and SV (scrambled vector). Aim 1c. Evaluate the effect of p-MMP-2 and irradiation alone, or in combination, on cerebral angiogenesis both in vitro and in vivo. Aim 1d. Determine the optimal doses of p-MMP-2 and irradiation alone, or in combination, on pre-established intracranial tumor growth or invasiveness of human glioblastoma cell lines injected intracerebrally in nude mice. Specific Aim 2. Determine the effect of p-MMP-2 and irradiation alone, or in combination, on the molecular mechanisms of proliferation, migration, adhesion and apoptosis in glioblastoma cell lines. Aim 2a. Investigate the effect of p-MMP-2 and irradiation alone, or in combination, on the molecular mechanisms of adhesion and migration in glioblastoma cell lines compared to control/mock and p-SV controls. Aim 2b. Determine the effect of p-MMP-2 and irradiation alone, or in combination, on the molecular mechanisms of proliferation in glioblastoma cell lines compared with mock and p-SV. Aim 2c. Evaluate the effect of p-MMP-2 and irradiation alone, or in combination, on the molecular mechanisms of apoptosis in glioblastoma cell lines compared with mock and p-SV. The proposed studies should generate major insights into the pathogenesis of radiation-induced alteration in tumor after inhibition of MMP-2 and, in turn, should suggest novel targets for therapeutic interventions of glioblastomas. PUBLIC HEALTH RELEVANCE: Despite the many therapeutic strategies undertaken for treatment of glioblastoma multiforme, the survival rate for patients afflicted with this aggressive cerebral malignancy remains low. Involved-field radiotherapy has remained the single most effective therapy of glioblastoma for more than 25 years. However, an increasing number of long survivors with secondary side effects from this treatment highlighted the need for development of novel therapeutic approaches. This proposal represents a combinational therapeutic approach using p-MMP-2 siRNA. This strategy may improve radiotherapy outcomes for the treatment of glioblastomas.